The present invention relates to methods and compositions for hydrogenolysis of carbon sugars and sugar alcohols and hydrogenation of lactic acid.
Currently, many of the chemicals in common use are derived from petroleum feedstocks. However, petroleum is present in limited underground reserves, and the extraction, transportation, and refining of petroleum can have severe environmental consequences.
Bio-based feedstocks, on the other hand, can be obtained from plants and can be processed by biological processes such as fermentation. To more fully utilize bio-based materials, it is often necessary to convert the fermentation products or other bio-based feedstocks into other chemicals that can be used in a variety of processes and products. Thus, it is an object of the present invention to provide new methods of converting sugars, sugar alcohols and other small molecules into a variety of desired chemical products.
For a long time, scientists and engineers have sought to convert sugars and sugar alcohols into other chemical products. For example, Conradin et al. in U.S. Pat. No. 2,852,270 (filed in 1957) reported that for increased production of propylene glycol, hydrogenolysis should be conducted over a Ni/Cu catalyst on a carrier such as magnesium oxide.
In U.S. Pat. No. 3,030,429 (filed in 1959), Conradin et al. stated that hydrogen splitting of saccharose to glycerol and glycols can be carried out in the presence of practically any technically feasible catalyst, provided that sufficient alkali is added to ensure a pH of 11 to 12.5. In one example, it was reported that hydrogenolysis of an aqueous saccharose solution over a nickel-on-kieselguhr catalyst proceeded with an 83% conversion to a product containing 43% glycerol and 25% propylene glycol.
Sirkar in U.S. Pat. No. 4,338,472 (filed in 1981) reported sorbitol hydrogenolysis to produce glycerol over a nickel-on-kieselguhr catalyst in which an alkali promoter was added to the feedstream to control pH and prevent leaching of nickel from the catalyst.
Tanikella in U.S. Pat. No. 4,404,411 (filed in 1983) described the hydrolysis of sorbitol and xylitol in nonaqueous solvents containing at least 10 mole % base. The catalyst used in the examples was nickel on silica/alumina. Distribution of ethylene glycol, propylene glycol and glycerol were reported.
Gubitosa et al. in U.S. Pat. No. 5,600,028 (filed in 1995) discussed the hydrogenolysis of polyhydric alcohols, such as sorbitol, over a ruthenium-on-carbon catalyst. In the examples, Gubitosa et al. reported that 100% of the sorbitol can be converted, with 41 to 51% of the product carbon atoms in propylene glycol.
Despite these and other efforts, there remains a need for new methods of converting sugars and sugar alcohols to smaller molecules that have a variety of uses. There is also a need for novel methods of converting molecules such as xylitol and lactic acid into higher value products such as propylene glycol and 1,3-propanediol. There is especially a need for new methods of such conversions that provide better yield and more desirable product distributions.
The invention provides a method of hydrogenolysis of an oxygen-containing organic compound, comprising: reacting an aqueous oxygen-containing organic compound with hydrogen at a temperature of at least 120xc2x0 C., and in the presence of a solid catalyst; where the solid catalyst comprises a Re-containing multimetallic catalyst, and where there is at least 25% as much Cxe2x80x94O hydrogenolysis occurs as Cxe2x80x94C hydrogenolysis. In some preferred embodiments, at least 100% as much Cxe2x80x94O hydrogenolysis occurs as Cxe2x80x94C hydrogenolysis. In some preferred embodiments, these percentages (such as 25%) refer to the total amount of hydrogenolysis, in other embodiments, they refer to rates, for example, the rate of Cxe2x80x94O hydrogenolysis is at least 25% as fast as the rate of Cxe2x80x94C hydrogenolysis. It has been surprisingly discovered that a Ni/Re catalyst is superior to other catalysts.
The present invention also provides a hydrogenolysis method in which a 6 carbon sugar, a 6 carbon sugar alcohol, or glycerol is reacted with hydrogen, at a temperature of at least 120xc2x0 C., and in the presence of a solid catalyst comprising a rhenium-containing multimetallic catalyst.
In a second aspect, the invention provides a composition of matter comprising: a solid rhenium-containing multimetallic catalyst; water, hydrogen; and a 6 carbon sugar, a 6 carbon sugar alcohol or glycerol.
In another aspect, the invention provides a method of improving the catalytic activity or selectivity of a supported metal catalyst for the reaction of hydrogen with a 6-carbon sugar, a 6-carbon sugar alcohol, or glycerol. In this method, rhenium is incorporated in a metal catalyst to form a rhenium-containing multimetallic metal catalyst. The Re-containing catalyst is reduced prior to, or simultaneous with a hydrogenolysis reaction. Preferably, the reduction is carried out by exposing the catalyst to hydrogen gas. Preferably, the 6-carbon sugar or a 6-carbon sugar alcohol is exposed to hydrogen and a rhenium-containing multimetallic metal catalyst under conditions sufficient to convert at least 40% of the sugar or sugar alcohol to propylene glycol, glycerol, ethylene glycol or any combination thereof. Here, xe2x80x9cimprovingxe2x80x9d means that at the same conditions where the rhenium-containing multimetallic catalyst results in 80% conversion, the yield of propylene glycol (xe2x80x9cPGxe2x80x9d) is improved by at least 5%, as compared with running the same reaction over each of: the same catalyst without rhenium, the same catalyst without rhenium but containing added weight of metal equal to the weight of rhenium in the improved method, and the same catalyst without rhenium but containing added moles of metal equal to the moles of rhenium in the improved method.
In yet another aspect, the invention provides a method of improving the reaction of hydrogen with a 6 carbon sugar or a 6 carbon sugar alcohol. In this method, the 6 carbon sugar, or a 6 carbon sugar alcohol is exposed to hydrogen and a rhenium-containing multimetallic metal catalyst under conditions sufficient to convert at least 40% of the sugar or sugar alcohol to propylene glycol, glycerol, ethylene glycol or any combination thereof. In this method, xe2x80x9cimprovingxe2x80x9d means that when tested with a 20 weight % glycerol in aqueous solution with 2 weight % sodium hydroxide, 1200 psi (8.2 MPa) hydrogen in a batch reactor for four hours, the yield of PG is improved by at least 5%, as compared with running the same reaction over each of: the same catalyst without rhenium, the same catalyst without rhenium but containing added weight of metal equal to the weight of rhenium in the improved method, and the same catalyst without rhenium but containing added moles of metal equal to the moles of rhenium in the improved method.
In another aspect, the invention provides a hydrogenolysis method in which a 5 carbon sugar, a 5 carbon sugar alcohol, lactate or lactic acid is reacted with hydrogen, at a temperature of at least 120xc2x0 C., and in the presence of a solid rhenium-containing multimetallic catalyst.
In yet a further aspect, the invention provides a composition of matter comprising: a solid rhenium-containing multimetallic catalyst, water, hydrogen, and a 5 carbon sugar, a 5 carbon sugar alcohol; lactate or lactic acid.
In another aspect, the invention provides a method of making propylene glycol, comprising: reacting a composition comprising lactate or lactic acid with hydrogen in the presence of a catalyst; where acid is added to the composition prior to the step of reacting; where the lactate or lactic acid is converted with a yield of at least 60%; and wherein the PG selectivity is at least 80%.
In a further aspect, the invention provides a method of improving the reaction of hydrogen with a 5 carbon sugar, a 5 carbon sugar alcohol, lactate or lactic acid. In this method, a 5 carbon sugar, a 5 carbon sugar alcohol, lactate and lactic acid is reacted with hydrogen in the presence of a solid, rhenium-containing multimetallic catalyst. In this method, xe2x80x9cimprovingxe2x80x9d means that at the same conditions where the rhenium-containing multimetallic catalyst results in 80% conversion, the yield of PG is improved by at least 5%, as compared with running the same reaction over any of: the same catalyst without rhenium, the same catalyst without rhenium but containing added weight of metal equal to the weight of rhenium in the improved method, and the same catalyst without rhenium but containing added moles of metal equal to the moles of rhenium in the improved method.
In a further aspect, the invention provides method of improving the catalytic activity or selectivity of a supported metal catalyst for the reaction of hydrogen with a 5-carbon sugar, or 5-carbon sugar alcohol, or lactic acid. The catalytic activity or selectivity of the supported metal catalyst is improved by incorporating rhenium in said metal catalyst to form a rhenium-containing multimetallic metal catalyst. The catalyst is typically reduced prior to or simultaneous with the reaction of hydrogen with a 5-carbon sugar, or 5-carbon sugar alcohol, or lactic acid. Preferably, the method also includes the step of exposing the sugar, sugar alcohol, or lactic acid to the rhenium-containing multimetallic metal catalyst under conditions sufficient to convert at least 40% of the sugar, sugar alcohol or lactic acid to propylene, glycal ethylene glycol or any combination thereof. In this method, xe2x80x9cimprovingxe2x80x9d means that when tested with 20 weight % xylitol in aqueous solution with 1 weight % sodium hydroxide, 1200 psi (8.2 MPa) hydrogen in a batch reactor until there is 80% xylitol conversion, the yield of PG is improved by at least 5%, as compared with running the same reaction over each of: the same catalyst without rhenium, the same catalyst without rhenium but containing added weight of metal equal to the weight of rhenium in the improved method, and the same catalyst without rhenium but containing added moles of metal equal to the moles of rhenium in the improved method.
The invention also includes methods of making 1, 3 propanediol by reaction of the starting materials described herein with hydrogen over Re-containing catalysts.
The invention includes any of the above aspects alone or in combination with any of the details in the following Examples and descriptions of preferred embodiments.
Various embodiments of the inventive methods have been found to provide numerous unexpected results that are superior over prior technologies, including: stability of the catalytic system, high conversions at relatively mild conditions, desired selectivities, high value product distributions such as high concentrations of propylene glycol, high PG selectivity at elevated temperature, production of 1, 3 propanediol, and process control to produce desired products.
The product mixtures that can be derived from the inventive methods offer advantages such as economy and environmentally-friendly derivation from fermented materials. These product mixtures can be used in various applications, for example, as anti-freeze.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.
xe2x80x9cRhenium-containingxe2x80x9d means that a solid catalyst contains at least 0.5 weight % Re, or that the catalyst contains a sufficient amount of rhenium such that when tested by hydrogenating a solution of 20 wt % sorbitol so that about 80% of the sorbitol is converted to shorter carbon chain products, the selectivity of the catalyst toward producing propylene glycol increases by at least 5% (where increases by 5% refers to absolute improvement, for example the propylene glycol selectivity increases from 20 to 25%.
xe2x80x9cMultimetallicxe2x80x9d means that the catalyst contains at least two metals (not including metals in the oxide support such as aluminum in alumina). In preferred embodiments, these metals function together to exhibit synergistic effects.
Carbon Molar Selectivity means the percent of carbon in a converted starting material (such as a converted sugar alcohol) that is the form of the selected species. For example, where a solution originally contains 1 mole sorbitol (i.e., 6 mole carbon as sorbitol), and the product contains 0.5 mole sorbitol and 0.25 mole PG (i.e., 0.75 mole carbon as PG), the PG carbon molar selectivity is 25%. In this case, the yield of PG is 12.5%. Unless indicated otherwise, the term xe2x80x9cselectivityxe2x80x9d in the present descriptions refers to carbon molar selectivity.